✅ Answer: Please refer to the following narrations:

1 مُحَمَّدِ بْنِ مُسْلِمٍ قَالَ سَمِعْتُ أَبَا جَعْفَر يَقُولُ لَا يَضُرُّ الصَّائِمَ مَا صَنَعَ إِذَا اجْتَنَبَ ثَلَاثَ [اربع] خِصَالٍ الطَّعَامَ وَ الشَّرَابَ وَ النِّسَاءَ وَ الِارْتِمَاسَ فِي الْمَاء

📚 *Al-Tahdhib, vol. 4, p. 189*

Muhammad ibn Muslim said: I heard Imam Baqir (peace be upon him) say: If a fasting person avoids three (or four) things, whatever they do will not harm their fast: eating, drinking, sexual relations, and immersion in water.

2 أَحْمَد بن أَبِي عَبْداللَّهِ عَنْ أَبِيهِ رَفَعَهُ إِلَى أَبِي عَبْدِ اللَّهِ قَالَ: خَمْسَةُ أَشْيَاءَ تُفَطِّرُ الصَّائِمَ الْأَكْلُ وَ الشُّرْبُ وَ الْجِمَاعُ وَ الِارْتِمَاسُ فِي الْمَاءِ وَ الْكَذِبُ عَلَى اللَّهِ وَ عَلَى رَسُولِهِ وَ عَلَى الْأَئِمَّةِ

📚 *Al-Khisal, p. 286, Hadith 39*

Imam Sadiq (peace be upon him) said: Five things break the fast: eating, drinking, intercourse, immersion in water, and intentionally lying about Allah, His Messenger, and the Imams (peace be upon them).

3 عَنْ عُمَيْرِ بْنِ مَامون وَ كَانَتْ بِنْتُهُ تَحْتَ الْحَسَنِ عَنِ الْحَسَنِ بْنِ عَلِيٍّ قَالَ: تُحْفَةُ الصَّائِمِ أَنْ يَدْهُنَ لِحْيَتَهُ وَ يُجَمِّرَ ثَوْبَهُ وَ تُحْفَةُ الْمَرْأَةِ الصَّائِمَةِ أَنْ تَمْشُطَ رَأْسَهَا وَ تُجَمِّرَ ثَوْبَهَا وَ كَانَ أَبُو عَبْدِ اللَّهِ الْحُسَيْنُ بْنُ عَلِيٍّ إِذَا صَامَ يَتَطَيَّبُ بالطيب وَ يَقُولُ الطِّيبُ تُحْفَةُ الصَّائِم

📚 *Al-Khisal, p. 61, Hadith 86*

Imam Hasan Mujtaba (peace be upon him) said: The gift for a fasting man is to apply scented oil to his beard and give his clothes a pleasant fragrance with incense or something similar.

The gift for a fasting woman is to comb her hair and give her clothes a pleasant fragrance with incense or something similar. Imam Hussain (peace be upon him) would use perfume while fasting and would say: Perfume and pleasant fragrance are a gift for the fasting person!

4 عَنْ أَحْمَدَ بْنِ الْحَسَنِ بْنِ عَلِیِّ بْنِ فَضَّالٍ عَنْ عَمْرِو بْنِ سَعِیدٍ عَنِ الرِّضَا قَالَ: سَأَلْتُهُ عَنِ الصَّائِمِ یَتَدَخَّنُ بِعُودٍ أَوْ بِغَیْرِ ذَلِکَ فَیَدْخُلُ الدُّخْنَةُ فِی حَلْقِهِ قَالَ جَائِزٌ لَا بَأْسَ بِهِ.

📚 *Al-Tahdhib, vol. 4, p. 324*

Amr ibn Said said: I asked Imam Reza (peace be upon him) about a fasting person who perfumes themselves with incense (which produces a pleasant smell when burned) or something else and the smoke enters their throat. The Imam said: It is permissible and there is no problem with it!

✅ According to the above narrations and others, the things that invalidate the fast are limited, and according to narration 3 , the gift of a fasting person is to apply fragrance to their body and clothes, and if, during the use of incense or Esfand or something similar, some smoke enters the nose, mouth, or throat, it does not invalidate the fast and does not cause any problem.

اللَّهُمَّ صَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْرَ